1. Field Of The Invention
Catalyst layers on ceramic carriers for converting exhaust gases from internal combustion engines
The invention relates to compact devices for post-burning and detoxicating the exhaust gases from internal combustion engines of road vehicles, especially in relation to supercharger units.
In particular it relates to a process for applying a catalyst layer composed of noble metals and/or noble-metal compounds to a carrier made of ceramic material.
2. Discussion Of Background
Catalysts for converting the exhaust gases of internal combustion engines (auto and diesel engines) are increasingly being used in particular for road vehicles, especially in view of the environmental pollution. The legal regulations in this connection are continuously becoming stricter and it is therefore in the interests of the general public to exploit 11 the possibilities for detoxicating exhaust gas. The following publications are cited in relation to the prior art:
Edgar Koberstein, Katalysatoren zur Reinigung von Autoabgasen (Catalysts for purifying vehicle exhaust gases), Chemie in unserer Zeit, Vol. 18, 1984, No. 2, pages 37-45 PA1 Polat Oeser and Walter Brandstetter, Grundlagen zur Abgasreinigung von Ottomotoren mit der Katalysatortechnik (Principles of purifying the exhaust gases from automobile engines using the catalyst technique), MTZ Motortechnische Zeitschrift 45 (1984), 5, pages 201-206 PA1 A.F.M. Leenaars, K. Kreize and A.J. Bruggraf, Porous alumina membranes, Chemtech Sep. 1986, pages 560-564 PA1 US-A-2,106,744 PA1 M.G. Nicholas and D.A. Mortimer, Ceramic/metal joining for structural applications (1985) The Institute of Metals), Materials Science and Technology, Sep. 1985, Vol. 1, pages 657-665 PA1 EP-A-0,143,956.
R.J. Charles, Phase Separation in Borosilicate Glasses, Journal of The American Ceramic Society-Charles, Vol. 47, No. 11, pages 550-563
EP-A-0,143,956 describes a volumetric supercharger unit (pressure-wave machine) for a road vehicle engine, which supercharger unit has a rotor which is also constructed as a catalyst carrier. This makes it possible to economize at least partly on a separate device for detoxicating the exhaust gases. However, problems arose in coating a rotor composed of a ceramic material since the rotor and, consequently, the catalyst layer are exposed to very high mechanical and thermal stresses (centrifugal forces, changes in temperature). The layers have to be securely anchored and must not peel off during operation.
There is therefore a considerable need for further development and perfection of the catalyst coating technology.